This invention relates to sputtering devices and in particular to such devices which are magnetically enhanced.
Disclosed in U.S. Pat. No. 3,878,085 granted to J. Corbani is a magnetically enhanced sputtering device having planar target cathodes. Heretofore, there has been concern over the relatively low utilization of the planar targets. Diode sputtering, which is not magnetically enhanced, gives very uniform erosion of the target, but is only capable of very low deposition rates. The addition of a suitably shaped magnetic field provides approximately 10 fold improvement in rates of sputtering--but the planar target typically erodes through at some point before more than about 30-40% of the total target has sputtered away. With targets of exotic or very pure materials this presents a serious cost problem. When considering the speed, uniformity, film structure, control ease, and freedom from contaminated wash water, etc., the magnetically enhanced sputter technique most often provides the best and most total cost effective films--in spite of the target utilization problem.
Several approaches have been proposed to reduce the target loss, typically these provide for movement of the magnetic field pattern by either mechanical or electromagnetic techniques. They do not appear to represent a totally effective solution to the problem, however, and do not direct one to the fundamental nature of the problem. Another approach has been to shape the target cross-section such that there is material present in proportion to the local erosion rates. This can increase the utilization percentage, but usually at great increase in target cost, to the point that this is not always a satisfactory answer. Magnetically enhanced sputtering is thus an effective coating technology that suffers from one major problem--the erosion pattern.